Heat shrinkable tubing has been used for a number of years to replace tape and other tedious means for protecting splices in cable and repair or pipe, etc. Commonly, the splice to be insulated or the pipe or cable to be covered is cut to permit the tube to be slipped over one segment followed by rejoining the cable or pipe, then slipping the heat shrinkable tube over the repair or splice. In many cases, however, it is not practical to slide a preformed tube over the splice or repair, it is useful to have a heat shrinkable member formed into a tube having an open longitudinal seam. Such a tube can be slipped around an existing splice or section of pipe or cable to be repaired eliminating the need to cut the cable in order to place the protective covering over it.
Heat shrinkable articles having such a tubular form have been disclosed in the literature as shown in U.S. Pat. No. 3,379,218. The method of closing the tube seam heretofore has consisted of some mechanical closure such as a metal rail, buttons, clamps, etc., to keep the two faces of the tube together during the heat shrinking process. A rigid mechanical closure has heretofore been found to be necessary because of the very high shear forces acting on the two ends which are held together during shrinking. While these mechanical closures have been successful in preventing the two edges from coming apart during heat recovery, they result in a bulky closure whose cross sectional area is much greater than wall thickness of the heat recoverable member. Therefore, during the heat shrinking or recovery process the wall of the tube becomes much hotter than the mechanical closure resulting in greater stress on the wall of the item during recovery which can lead to a split in the recovering portion. Other disadvantages of mechanical closures are the fact that sealants normally coated on the inner wall of these heat recoverable articles are not all melted to the same degree because there is a much greater heat sink in the mechanical closure area preventing the sealant under this area from reaching the same temperature as the sealant under the thinner wall section with the result that the sealant under the closure is often not melted sufficiently to form a good bond with the cable or pipe being repaired and a leak often results in this area, and the further fact that bulky mechanical closures project out from the cable or pipe being repaired and when the cable or pipe is pulled through a conduit, or along the ground, the closure can snag and prevent the cable or pipe from freely moving in the manner desired.
It is the object of the present invention to provide a chemical means of sealing two edges of a heat shrinkable or recoverable article to form a tubular member around the item on which the tubular member is to be shrunk for purposes of repairing a leak, sealing a splice or junction of two cables, etc.
It is a further object of this invention to provide a rapid method of sealing the two ends of a heat recoverable article without recourse to mechanical means for holding the ends together.